a. Field of Invention
This invention relates to novel di- and tetra- (t-alkylperoxy) acetals and ketals, and to their use as free-radical initiators in polymerizations of ethylenically unsaturated monomers, as curing catalysts for unsaturated polyester resins and as curing, crosslinking or vulcanizing catalysts for .alpha.-olefin polymers and copolymers.
B. Related Art
As a class of peroxides, diperoxyketals (and diperoxyacetals) have been known for more than two decades (U.S. Pat. No. 2,455,569) and, during this time, these peroxides have found use as initiators in vinyl polymerizations, as catalysts for vulcanizing rubbers and as curing agents for polyethylene and ethylene/.alpha.-olefin copolymers (see U.S. Pat. Nos. 2,650,913; 2,656,334; 2,692,260; 2,698,311; 3,275,714; 3,296,184; and 3,468,962; Dutch application Ser. Nos. 6,403,775, Jan. 25, 1965, C.A. 62 P 14854 a. and 6,404,319, Apr. 21, 1964, C.A. 64, P 11426 h; Z. F. Nazarova et al., Zhurnal Organicheskoi Khimii, vol. 2, No. 2, pp. 259-61, February 1966; and O. M. Mashnenko et al., Vysokomol. Soedin., Ser. B.9 (10), 755-7 (1967) Russ.).
However, most of the diperoxyketals (and diperoxyacetals) reported in the patents and literature and/or commercially available are di(t-butylperoxy) ketals (and acetals) prepared from ketones (and aldehydes) and t-butyl hydroperoxide (as shown in the early 2,455,569 U.S. patent). The above cited Mashnenko et al. article did some studies with t-amyl and t-hexyl hydroperoxides and found that the rates of polymerization of styrene using the di(t-amyl and t-hexylperoxy)hexane derivatives were similar to that of di(t-butylperoxy) hexane (1.09: 1.20: 1, respectively).
U.S. Pat. No. 3,488,392 and German OLS No. 1,923,085 describe various substituted diperoxyketals.